Hydraulic dashpot



OC- 8, 1963 J. M. cLAPP HYDRAULIC DASHPOT 2 Sheets-Sheet 1 Filed June l2, 1962 INVENTOR JOHN M. Cl. APP

BY @MAX @.T'm HIS ATTORNEY Oct. 8, 1963 J, M, CLAP'P 3,106,267

HYDRAULIC DASILIPOT Filed June 12, 1962 2 Sheets-Sheet 2 7 lo le 13" a f 35 NvENToR JOHN vfr. C/ PP @14 wrm H l S ATTORNEY forms the job that it was designed for.

United States Patent j 3,106,267 HYDRAULIC DASHPOT John M. Clapp, Athens, Pa., assigner to Ingersoll-Rand JCompany, New York, N.Y., a corporation of New ersey Filed June 12, 1962, Ser. No. 202,019 6 Claims. (Cl. 18S- 97) This invention relates to a hydraulic dashpot for use with many different types of mechanism for controlling and regulating the speed or rate of movements of such mechanisms.

,Conventional hydraulic dashpots usually are subject to leakage of the hydraulic fluid. Eventually, such loss of hydraulic iiuid undesirably changes or modifies the operation of the dashpot so that it no longer effectively per- Hence, the hydraulic fluid in conventional dashpots must be occasionally checked and replenished, where required, to insure the proper and intended type of operation of the dashpot. One problem with conventional dashpots is that they undesirably change their operation after only a relatively small loss of hydraulic liuid. Another problem with conventional dashpots is that they usually do not provide any way for easily checking the amount of hydraulic fluid to determine whether or not replenishment of the iiuid is necessary. Further problems include: conventional dashpots having a variable control means are plagued with dirt getting into the hydraulic system, either through internal wear or by the addition of dirty hydraulic fluid; conventional dashpots usually do not have a long stroke which can be regulated or adjusted; and conventional dashpots are not satisfactory for use with an air feed drill to provide the drill with a stroke including a rapid approach portion and a slow drilling portion.

The principal object of this invention is to eliminate or substantially minimize the above problems.

Other important objects include: to provide a hydraulic dashpot which is not undesirably affected by loss of a minor portion of its hydraulic fluid; to provide a hydraulic dashpot which can be easily and quickly checked for determining the amount of hydraulic fluid contained in the dashpot and whether or not such Huid needs replenishing; to provide a hydraulic dashpot which can lose a relatively large amount of its fluid before its operation is changed; and to provide a hydraulic dashpot which is particularly adapted for use with a reciprocating tool such as an air feed drill. j

n in brief, certain of the objects .of this invention are attained by providing a dashpot with means for storing an l excess or reserve capacity of hydraulic fluid, over and above the amount that the dashpot normally needs and uses in its operation and providing Vthe dashpot with means for automatically feeding the reserve hydraulic fluid into the operating fluid chambers of the dashpot as leakage of the fluid occurs. Other objects of the invention are attained by providing the dashpot with a signal means which clearly indicates the amount of reserve hydraulic fluid contained in the dashpot, so that replenishment of the duid is indicated when the reserve fluid chamber in the dashpot is empty.

The invention is described in connection with the drawings wherein:

FIG. l is an elevational view of an embodiment of the invention installed on an air feed drill, the air feed drill being shown in simplified or diagrammatic form;

FIG. 2 is lan enlarged longitudinal view of the dashpot embodiment in FIG. 1 with parts being broken away;

FIG. 3 is a rear end view of FIG. 2 taken on the line 3-3 of FIG. 2; i FIG. `4 is an enlarged section taken on the line 4 of FIG. 3; and

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FIG. 5 is an enlarged view of a portion of FIG. 2 with the Yhydraulic reservoir fluid indicator shown in its ful-l position.

The embodiment of dashpot 1 shown in the drawings is designed for use on an air feed drill 2, such as is shown in simplified form in FIG. l, to control and regulate the forward feeding movements of its drill bit 3. The air feed drill 2 is conventional and includes a body, also designated 2, a rotary motor 4, shown in dotted lines, driving the drill bit 3 and a pneumatically actuated piston 5, also shown in dotted lines, for feeding the motor 4 and drill bit 3 axially forward and then returning these elements rearwardly. The piston 5 is connected to a follower rod 6 which reciprocates with the piston 5 and projects rearwardly from the drill body 2 where it is adapted to interengage the operating mechanism of the dashpot 1.

The dashpot 1 is adapted to be mounted on the side of the drill body 2 and includes an elongated hollow body 9 containing av cylindrical bore 10. A plunger or piston 11 is slidably mounted in the bore 10 and is fixed or integral with a piston rod 12 which extends rearwardly from the piston 11 and projects rearwardly from the dashpot body 9. The piston 11 carries a flexible cupped washer 13 on its front face for sealing purposes and is connected to a piston rod extension 14 which extends forwardly from the piston 11 through the forward portion of the dashpot body 9.

The piston 11 separates two hydraulic fluid chambers in the dashpot body 9. These includeV a front chamber 15 and a rear chamber 16. The front end of the front chamber 15 is closed by an annular wall 17 which fits in the front end of the dashpot body bore 10 and embraces the piston rod extension 14. The annular wall 17 is provided with a suitable O-ring 18 for sealing purposes. A coil spring 19 is disposed in the front chamber 15 between the annular wall 17 and the piston 11 for biasing the piston to its rear position, as shown in FIG. 2. l

As the piston 11 is moved forward in the bore 10, the volume of the front chamber 15 is progressively reduced while the volume of the rear chamber 16 is progressively increased. This dashpot 1 is designed so that the amount of decrease in volume of one chamber will be accompanied by an increase in volume of the other chamber by substantially the same amount, whereby the sum of the volumes of the two chambers 15 and 16 remains the same throughout a stroke of the piston 11.

Means is provided for adjustably restricting and controlling the flow of hydraulic uid from the front chamber 15 to the rear chamber 16 during a forward stroke of the piston 11. This means includes a front passage 21 extending rearwardly through the dashpot body 9 from the front chamber 15, a threaded needle valve 22 fitting into the rear of the front passage 21 to vary and restrict the flow from the front passage 21 and an escape passage 23 running from the needle valve 22 to the rear chamber 16. The flow of hydraulic uid from the front passage 21 is varied by turning the needle valve 22 in its threaded hole to move its needle nose inwardly or outwardly in the rear end of the front passage 21, depending on whether the flow is to be decreased or increased. The needle valve 22 dumps the fluid into the escape passage 23, whence it ows freely into the rear chamber 16.

A porous filter sleeve 25 ii-ts in the front chamber over the inlet of the front passage 21 to bar and prevent dirt -in the hydraulic uid from entering the front passage and interfering with theneedle valve 22.

yCheck valve means -is provided for allowing the hydraulic fluid to return easily from the rear chamber 16 to the front chamber 15 during the return stroke of the piston 11. This means includes a ball check valve 27 contained in the piston 11 and communicating between the opposite faces of the piston 11. This communication is provided by various passages drilled in the piston rod 12, the piston 11 and the piston rod extension 14, all of which are clearly shown in FIG. 2.

The dashpot 1 is charged with hydraulic fluid through a conventional check valve fitting 29 similar to the Alernite fitting used for greasing machine bearings. The fitting 29 is threaded into a charging passage 30 which leads into the escape passage 23, as shown in FIG. 4. A porous filter 31 is placed in the passage 36 for filtering hydraulic fluid as it is fed to the dashpot. When not being used, the fitting 29 is covered with a rubber cap 32 to bar dirt from it.

Means is provided in the rear chamber 16 for storing an excess or reserve amount of hydraulic fluid therein for use in replacing lthe gradual loss of hydraulic fluid from the dashpot, caused by leakage which occurs in most dashpots. This reservoir means includes a sleeve 34 slidably embracing the piston rod 12 and an enlarged front end 35 which forms the rear end of the rear chamber 16. Moving the sleeve 34 rearwardly yincreases the volume of the rear chamber 16, as shown in FIG. 5, thus allowing the rear chamber 16 to hold an additional quantity of hydraulic fluid, over and above the amount of hydraulic fluid necessary for operation of the dashpot.

The sleeve 34 slides in a bushing 36 fixed in the dashpot body 9 adjacent its rear end and a coil spring 37 encircles the sleeve 34 between the bushing 36 and the enlarged front end 35 of the sleeve 34 for biasing it forward. Sufficient sealing means is installed between the sleeve 3f. and the adjacent parts of the dashpot to substantially prevent fluid leakage from the dashpot.

As the sleeve 34 moves rearwardly in the dashpot body 9, it is long enough to project progressively rearwardly from the rear end of the dashpot body 9. The word empty is printed on the piston rod 12 where it is normally visible when the dashpot is empty of hydraulic fluid and the piston 11 is fully retracted. The rear end of the sleeve 34 is arranged to cover the sign empty on the piston rod 12 as the sleeve progresses rearwardly, thus, indicating that the dashpot is no longer empty. Also, a sign full is printed on the sleeve 34 where it gradually is exposed as the sleeve progresses rearwardly. The sign full is located to be fully exposed as shown in FIG. when the dashpot is fully charged with hydraulic fluid.

The sleeve 34 serves both as a means for providing a reserve reservo-ir of hydraulic fluid to the dashpot 1 and as a signal means for indicating the amount of additional fiuid contained in the dashpot.

The rear end of the piston rod 12 is threaded and carries a fork 39, threaded thereon, which is adapted to er1- gage the follower rod 6, as shown in FG. 1. Thus, the forward movement of the follower rod 6 of the air feed drill 2 is transmitted to the piston rod 12, resulting in the dashpot 1 limiting the forward stroke of the air feed drill to a regulated and selected rate of speed.

Operation Prior to using the dashpot 1, it is charged with hydraulic fluid through the charge fitting 29 using a suitable pressure applying tool, which might, for example, take the for-m of a conventional grease gun. As the fluid is pumped into the dashpot, it flows, in sequence, through the charge passage 30, the escape passage 23, into the rear chamber 16, through the ball check valve 27 and into the front chamber 15. Eventually, the front chamber 15 is filled and, thereafter, additional fluid begins driving the sleeve 34 rearwardly. Rearward movement of the sleeve 34 covers the sign empty on the piston rod 12. and progressively exposes the sign full on the sleeve, as seen in FIG. 5. When the sign full is completely exposed, the operator knowns that the dashpot is full and discontinues feeding fluid to it. The dashpot is now ready for use.

The dashpot 1 is attached to the air feed drill 2 in an operative position -and with the fork 39 on the dashpot piston rod 12 straddling the follower rod 6 of the air feed drill. As the air feed drill 2 moves on its forward stroke, the follower rod 6 drives the piston rod 12 forward in the dashpot body 9. The forward movement of the piston 11 drives the hydraulic fluid through the filter 2.5 and into the front passage 21 to the needle valve 22. The needle valve 22 controls the rate of escape of the fluid from the front chamber and, thus, limits and controls the speed of the forward movement of the piston 11 which in turn limits and controls the forward feed speed of the air feed drill 2. Adjustment of the needle valve 22 will vary the fluid escape rate and, therefore, vary the forward feed speed of the air feed drill 2.

When ythe air feed drill 2 reaches the end of its forward stroke, it quickly returns unhindered by the dashpot 1. As the forward force on the piston rod 12, exerted by the air feed drill 2, is released, the coil spring 19 returns the dashpot piston 11 rapidly while the hydraulic fluid in the rear chamber 16 passes freely through the ball check valve 27 into the forward chamber 15. Hence, the return stroke of the dashpot piston 11 is substantially unhindered by the hydraulic fluid contained in the dashpot.

Over a period of time, the hydraulic fluid gradually leaks from the dashpot and, as this loss occurs, the sleeve 34 biases the reserve fluid in the rear chamber 16 forwardly to take the place of the lost fluid. Eventuali` the sleeve 34 will move forward enough for the sign full to be covered, as shown in FlG. 2, and the sign empty, on the piston rod 12, to be exposed. When this happens, the operator knowns that it is time to recharge the dashpot again.

It `will be understood that although only one embodiment of the invention is specifically described, the invention may embrace various other embodiments which are obvious from an understanding of the described embodiment `and are embraced within the claims of the invention.

Having described my invention, I claim:

l. A hydraulic dashpot for use in controlling the movements of tools, comprising: an elongate hollow body forming a cylinder; a piston movably mounted in said cylinder to form first and second chambers therein separated from each other by said piston; a piston rod connected to said piston and extending entirely through bot of said chambers with an end portion projecting from at least one end of said body, said projecting end portion adapted to be connected to a tool for regulating its movement; Variable restriction means for allowing hydraulic fluid to flow from said first chamber to said second chamber and operative to regulate the rate of said ow of hydraulic fluid; check valve means for allowing hydraulic fluid to flow freely from said second chamber to said first chamber; a displaceable follower sleeve slidably mounted on said piston rod and in said cylinder adjacent said second chamber with the inner end of said sleeve serving as the outer end of said second chamber so that the movement of said sleeve in said cylinder results in varying the volume of said second chamber; spring means biasing said sleeve inwardly to reduce the volume of said second chamlber whereby said sleeve can be displaced by the addition `of hydraulic fluid to said chambers for storing a reserve quantity of hydraulic fluid therein; and said outer end of said sleeve adapted to progressively project from an end of said cylinder as it moves outwardly for indicating the position of the inner end of said sleeve, thereby indicating the amount of reserve hydraulic fluid contained in the cylinder.

2. The hydraulic dashpot of claim l including indicia mounted on said sleeve where it is exposed by said outward movement of the sleeve for indicating that the dashpot is substantially full of fluid.

3. The hydraulic dashpot of claim 1 including indicia located on said piston rod in a position to be covered by the `outward movement of said sleeve, so that the exposure of said indicia indicates a loss of fluid from the dashpot.

4. The hydraulic dashpot of claim 3 including indicia mounted ion said sleeve Where it is exposed by said outward movement of the sleeve `for indicating that the dashpot is substantially full of fluid.

5. The hydraulic dashpot of claim l including la filter cooperating with said variable restriction means for preventing dirt in the hydraulic fluid from interfering with said variable restriction means.

6. The hydraulic d-ashpot of claim 5 wherein said check valve means is mounted in said piston and communicates between opposite faces ofthe piston.

References Cited in the le of this patent UNITED STATES PATENTS Thompson July 10, 1923 OConnor et al. n Aug. 14, 1956 Gies Oct. 20, 1959 Born et al. Aug. 9, 1960 Manna May 8, 1962 FOREIGN PATENTS `France Apr. 28, 1958 France Mar. 10. 1954 

1. A HYDRAULIC DASHPOT FOR USE IN CONTROLLING THE MOVEMENTS OF TOOLS, COMPRISING: AN ELONGATE HOLLOW BODY FORMING A CYLINDER; A PISTON MOVABLY MOUNTED IN SAID CYLINDER TO FORM FIRST AND SECOND CHAMBERS THEREIN SEPARATED FROM EACH OTHER BY SAID PISTON; A PISTON ROD CONNECTED TO SAID PISTON AND EXTENDING ENTIRELY THROUGH BOTH OF SAID CHAMBERS WITH AN END PORTION PROJECTING FROM AT LEAST ONE END OF SAID BODY, SAID PROJECTING END PORTION ADAPTED TO BE CONNECTED TO A TOOL FOR REGULATING ITS MOVEMENT; VARIABLE RESTRICTION MEANS FOR ALLOWING HYDRAULIC FLUID TO FLOW FROM SAID FIRST CHAMBER TO SAID SECOND CHAMBER AND OPERATIVE TO REGULATE THE RATE OF SAID FLOW OF HYDRAULIC FLUID; CHECK VALVE MEANS FOR ALLOWING HYDRAULIC FLUID TO FLOW FREELY FROM SAID SECOND CHAMBER TO SAID FIRST CHAMBER; DISPLACEABLE FOLLOWER SLEEVE SLIDABLY MOUNTED ON SAID PISTON ROD AND IN SAID CYLINDER ADJACENT SAID SECOND CHAMBER WITH THE INNER END OF SAID SLEEVE SERVING AS THE OUTER END OF SAID SECOND CHAMBER SO THAT THE MOVEMENT OF SAID SLEEVE IN SAID CYLINDER RESULTS IN VARYING THE VOLUME OF SAID SECOND CHAMBER; SPRING MEANS BIASING SAID SLEEVE INWARDLY TO REDUCE THE VOLUME OF SAID SECOND CHAMBER WHEREBY SAID SLEEVE CAN BE DISPLACED BY THE ADDITION OF HYDRAULIC FLUID TO SAID CHAMBERS FOR STORING A RESERVE QUANTITY OF HYDRAULIC FLUID THEREIN; AND SAID OUTER END OF SAID SLEEVE ADAPTED TO PROGRESSIVELY PROJECT FROM AN END OF SAID CYLINDER AS IT MOVES OUTWARDLY FOR INDICATING THE POSITION OF THE INNER END OF SAID SLEEVE, THEREBY INDICATING THE AMOUNT OF RESERVE HYDRAULIC FLUID CONTAINED IN THE CYLINDER. 